Microphone button



Nov. 10" 1925.

W. H. BARBER rucnoruom: BUTTON Filed D00. 15. 1921 2 Sheets-Sheet ALL/ m Nov. 10,1925. 1,560,643

W. H. BARBER MXCROPHONE BUTTON Filed D90. 15. 1921 2 Sheets-Sheet 2 Patented Nov. 10. 1925.

UNITED STATES P TENT OFFICE.

WALTER H. BARBER, OF MELROSE, MASSACHUSETTS, ASSIGNOR TO SUBMARINE SIG- Y HAL COMPANY, OF PORTLAND, MAINE, A CORPORATION OF MAINE.

' by one ship of ,S1

MICROPHONE BUTTON.

Application filed December 15, 1921. Serial No. 522,500.

To all whom it may concerns Be it known that I, \VALTER H.- BARBER, of Melrose, in the county of Middlesex and State of Massachusetts, a citizen of the United States, have invented a new and useful Improvement in Microphone Buttons, of

which thefollowing is a specification.

This invention relates to a receiving instrument for the deltection 'of submarine articular to the receptionthe use of any one of a number of designs of watertight cases commonly called hydrophones containing granular carbon microphone vbuttons. In practice the various acoustic devices have proved too weak for use beyond a limited range. The electromagnetic devices have also proved weak unless used with an amplifier. Moreover, these devices possess an inherent pitch which changes or alters the, characteristics of the.

incoming sound so that the incoming sound is frequently distorted and unnatural in quality.

The commonest method of detecting signals has been by the use of a hydrophone,

the form of wh ch has varied according to the type of signal to be received. Frequently, as in the case of submarine fog bells, the signals are all of the same pitch, and the detecting hydrophones have been designed to-respond 'inost'readily to that pitch. In other cases, where the, signal was the noise of a distant, perhaps hostile, ship, the watertight case or at least the active diaphragm of the case has been made of rubber in order that the characteristics of: the signal may be transmitted as nearly as possible without distortion.

While a single hydrophone may be used successfully to detect a sigpal, it has been customary to use the ydrophones in matched sets of two or more instruments possessing the same pitch, or the same sensitiveness or the same rapidity of response to an incoming signal ora combination of theseor other characteristics. One of the principal difiiculties in the practical manufacture. of hydrophones has been that ofv producing microphone buttons sufficiently uniform in their characteristics to admit of ra id and exact matching of the complete iydrophones into the necessary sets. This is particularly true when the hydrophone is intended for use in the detection .of signals originating 111 sources which do not have the same pitch, and in the detection' of ships. lVhat is needed is'a button which can be manufactured so that sets of similar buttons can be easily obtained; in

which all the buttons in a setshall possess similar characteristics at a given frc-' quency, and the same characteristics at all frequencies in the practical range, say-from In the effort 300 to 5,000 cycles per second. to supply this need some microphone buttons have been designed so as to be highlydamped. In such buttons the natural pitch is pretty well eliminated, and the buttons respond with more or less uniform intensity at all frequencies, but such buttons are of necessity comparatively Weak,-since so much of the available energy is absorbed'by the damping members. I It has also been sought to obtain the desired result by supporting the inertia ,ele-' ment of the nqierophone button by the use- 'of SOlllGlIlClfiSilC substance such as paper,

cloth or felt. Buttons of' this type have proi'edtco weak for practical use. Rubber has also been tried as the elastic material for the support ofthe inertia element of the button. Satisfactory results have been obtained by the use ofrubber, but'mechanical difficulties in the assembly of the button, due

to the tendency of rubber to creep when clamped under pressure, have prevented the assemblyof uniform buttons using this material. I

In my invention I have adopted a combination ofthe damping method with the use of rubber as the supporting material for the inertia member ofthe button; I The button is of the common design, in'which two electrodes of conducting imaterial, referably polished carbon, are mounte with granular carbon between them. I supply the necessary amount of damping by lacing a perforated felt washer under si ht pressure between the carbon electro es.

The cavities in this washer serve to hold the. granular carbon between the electrodes. One of the electrodes is mounted in a metal cup, preferably by soldering, while the other is attached to a'slightly larger rubberqcup in any one of several methods hereinafter described.

My invention will be understood by reference to .the drawings in which Figure l is a sectional view'of the parts in their relative positions unassembled.-

Fig. 2 is a plan view ofthe felt washer I or spacer.

- phone.

In the bottom ofa metal cup 1 is fastoned an electrode 3 of highly polished nontarnishing metal, or preferably polished car bon, by means of a drop of solder 4. The metal cup 1 is provided with a narrow flange 2 and is perforated withsex'eral holes 101 which provide free circulation of air tion of the button -diaphragm by the increase of air pressure within the hydrophone v for cooling the button and. prevent distorease when it is submerged at a-considerable depth. The circular felt washer 5 is pcrforated withelongated cavities 6, which are "nearly full of granulated carbon 7. It fills the space between the electrode 3 and a sec ond electrode 8 under a pressure determin .y'the amount of damping'desired ll'tti'l. button.

,Experiment has shown that, when but-v ton containing this type of chamber for the carbon is mounted with the chambers or slotsin a horizontal position, it will be much' more uniform in sensitiveness than the ordinary type of button.

The second electrode E4 which may be of polished-non-tarnishable metal, but is preferably of polished carbon, is soldered to a metal disk .9, provided with a stud 91 havinga shoulder 10 and a threaded shank 11. A

moulded rubber cup 121 has a recess 13 designed to fit over shoulder 2 on cup'l when thebutton is assembled, and also a central hole 14 of such size as to just pass over the shoulder 10 and rest against the back of the disk 9. The cup 121 fits over the metal cup 1 and its side Walls enclose the cup 1. The

bottom 12 of the rubber cup serves as the diaphragm or active elastic supporting element for the inertia part of the button. A clamping member or washer 15 has a smooth hole 16 which just fits over the shoulder 10. The combined thickness of the diaphragm 12 and clamping member 15 is greater than sulated' 'pin'21.

the height of the shoulder 10 so that a; locknut 17 with a threaded hole 18 maybe apq plied to the threaded stud 11 to clamp the,

rubber diaphragm 12 with a definite pressure between the metal disk 9 and the clamping member 15. This pressure may be con.

trolled by tightening nut 17 with a socket wrench employing'a frictiongrip which releases at a predetermined fpressure.

In assembly the felt washer 5 is placed in the cup 1 against the electrode 3, and the slots 6'are filled with the necessary amount of granular carbon 7. The shoulder 10 of the second electrode stud 91 is then passed other or additional means may be usedsuch as whipping or cementing. I prefer to mount the button in a square frame 19 con- Pin 20 is taining two pins 20 and 21. grounded electrically upon the yoke, while pin 21- is insulated from it by a bushing 22 of-insulating material. The shank 11 elec-' trically connected with the electrode 8' is screwed into the threaded nut 23 on the outside of thefram'e'lt), while the other elec-- trode't) is connected by wire 24 with the in- Thepurpose of this yoke 19 is to provide mechanical protection to the button in andling, and to take up the strain of the lea wires 25 by means of which the -..tton is connected with the outside electrical circuit.-- The exact manner of the use o-f this'yoke is shown in Fig. 8.- This yoke 19 may be omitted if the lead wires 25 are. snfiieiently soft and flexible, or another form.

may be used to obtain the sameresults.

Figs. 4 and 5 show two methods of moulding the rubber cup and the electrode mount in one unit, so that the rubber need be under no strain except that due to the weight of the inertia element which it supports. In Fig. 4 the rubber is vulcanized under pressure between the disk 9 and a flange 151' earryingthe'shank 11. In Fig. 5 the rubber entirely surrounds a disk 152 and fills holes 153 so as to give a firm union between the rubber and the' metal. In this case the threaded shank 11 stops at shoulder 154 so that the button may be mounted firmlyon its support without exerting pressure on the rubber.

Figs. 6 and 7 show an alternative method of assembling the rubber cup 121 and the electrode stud 91. The metal stud consists as before of a disk 9 to which the electrode 8 is attached, and having a shoulder 10 and a threaded shank 11. The clamping washer 26 is of a diameter less than that of disk and has Saree or more 27 slm ootl lo boar on the rubber 1 1r mixer poin liar. positive and at break up any natural Vwrntions. of lilo rub oer (liapllmgnr Furtl'mrnn the shape of the feet ma" be (lemgned as to produce a minimum riisrortim'l of tho noer due "to pressure.

Fig. 8 shows one of the buttons mounted in a common type of l1 -'r.lro li me case. A gum rubber cup PflSSQLi ovor a cylinilririul metal sleeve: "29. the joint bot-ween them being lllxllf? wnwrl'ight by renivnt 21ml a olaznpilng band. An anchor not 3.1 is

moulded into the botiom of tho insirie of the rubber cup 28 and serves as a support for the button which is a'ilixrcl to in by.

the threaded shank ll, 511e, frame 19 being used or not desired. The elect-rival rounoetion of the button with the onlszrlo circuit is provider through two LiililPS 32, 32 and two leads 2-5, .25 one counovied to the lnsanlatecl pin 2 and tho other with lire grounded pin 20 and yoke 19. all as above deonribod. The. nobles 33L 32 are val into tlu? hollow climnlmr 253 through a sl-xtulling box 35, thus making tho clnnnber :33 warm-- tight. A second rubber men'lber 3G is panned 0W1 the rear end of tho metal slwve 2 to make the assembly more synnnclrical and form of button nmy be 5 upon the skin of tin; sh p 1 o usual forms of hyd m llions o her lo mountit for the j comznuni-failons from than many of the types now known, and in addition is practically i from n nai -1n? period of iis own, pq'nl .ing it- 'to rm; owl will; equal facility to ulgnnls of dlilereni ournos and to reproduvo the noise of "liolnnt ships without distortion.

In (he speci fication above I have doscriluwl the button in all. cases mounted by the stud panning through the rubber diaphragm, but I do not limit myself in this respect, since equally good results have been obtained when the button is mounted by a stud atinched to the metal cup. I have also describerl the cup-sl1opecl diaphragm of the bmlon and the two out-er members of the nose:- as being maria of pure gum rubber, but any natural or synthetic material possessing lsir nilnr cliarncterist-ics may be used and the term ruhber as used in the claims is intended to include similar mote rial. v

'Wlult I claim as mf invention is:----

l. A microphone button compr'sing twoolmrtroilo granular carbon located beta-wen hillll eleodors and un unstretclwl rulabor diaphragm, one of said electrode-s being vlnmperl to Sflltl diaphragm.

A microphone button comprising a metal cup having an. electrode attached thereto ami a rubber cap comprising a vibrw lory dianhragm and a flange pro'ecting tllerefronn a second electrode attaclled to said diaphragm to vibrate therewith, and granular cronducting material located 09- tw'oon said electrodes.

3 A. microphone button comprising two electrodes, means for holding granular can oon between them, said granular carbon, 2; rubber diaphragm a disk bearing a tl'n'onded stud, a clamping spider having a plu- I'alil-y of feet, and :1V lockout, one of said elesfirodes being attached to said disk, and said siiurl being passed through holes in the rubber diaphragm, clamping washer and l'ocknut, whereby the tightening of the locknul; causes the rubber diaphragm to be clmnpod between said spider and the disk with a minimum distortion of the rubber.

l. A microphone but-ton comprising an unstrotched rubber diaphragm and two electrodes, one of said electrodes being mounted upon said diaphragm who day said buf'son will have a low natural pitrla.

A n'licrophono button vonlprising Till)- ul. two olectrorles ono of ll electrodes having one surinco abutting rfaoe of said diaphragm anal being Trlnly clumped thereto;

V1 ALTER H. Bill-181E722.

Fail 

